The meeting focused on how to prepare for hypothetical terror scenarios, like mass casualties and multiple shooters in Chicago.

"There is no viable threat over the City of Chicago," Rahm Emanuel said.

And yet, Chicago's top law enforcement officials - local, state and federal - gathered behind closed doors to discuss the very real possibility that a Paris-style terrorist attack could happen here.

"We are going to be alone when it happens. That's a fact. It's going to happen. It's going to. This is middle America," said Jose Santiago, Chicago Fire Department Commissioner.

"What happens when we have a multiple-shooter incident? Does everybody immediately go to the scene? Or is there something we can communicate to our soft target? In other words, working with the civilian population to give them direction," Chicago Police Department Supt. Garry McCarthy said.

Over 200 counter-terrorism experts and first responders ran through possible scenarios including a mass casualty event with hundreds dead or injured throughout the city. They discussed tactics and how the evolving nature of these attacks has changed the way law enforcement needs to respond. The taking of the concert hall in Paris and subsequent massacre was put up as an example of that.

"We can't use the tactics we used in the past where we surround, contain, talk and try to negotiate. We're going to be in a combat situation if these things happen," McCarthy said.

But is Chicago ready for such an eventuality? One of today's speakers described this as a city rich in soft-targets. Another called Chicago, "a prime target". University of Chicago terrorism expert Prof. Robert Pape says it all comes down to advance preparation, as was seen on display in Paris.

"Within a fairly short period of time, the police and other first responders operated in a fairly coordinated way minimizing the chaos and doing a terrific job under the circumstances," Pape said.

The mayor's office said the counter-terrorism workshop was organized long before the terror attacks in Paris. Officials said there is no specific threat to Chicago.

"The tragic events in Paris really brought home the possibility and probability of some kind of catastrophic event in the United States and most importantly, certainly, near and dear to us, the city of Chicago," said Gary Schenkel, Executive Director, Office of Emergency Management and Communications.

The two-day workshop continues on Wednesday. Most of the meeting was closed to the media in an effort to protect strategy sessions from being made public.